Uniform speed system



Jan. 5 19 37.

E. JANETSCHKE UNIFORM SPEED SYSTEM Filed March 3, 1934 INVENTORErwnJbnefac/vke.

WITNESSES a 6. I ATTORNEY Patented Jan. 5, 1937 UNITED STATES PATENTOFFICE UNIFORM SPEED SYSTEM Application March 3, 1934, Serial No.713,841

In Germany March 6, 1933 2 Claims. (Cl. 172-293) My inventionrelates tospeed regulating systems and particularly to such regulating systems fora plurality of motors that are required to operate in a predeterminedspeed relationship.

In a'number of motor applications, such as for driving the severalsections of a paper making machine, a continuous wire rolling or drawingmill, etc., it is required that the several parts of the machine drivenby separate section driving motors shall operate in a fixed speed ra io.

My invention contemplates the use of controlled rectiflers for thecontrol of theindividual motors driving the several sections of amachine. Grid controlled gas or vapor filled discharge devices arepreferably used as rectiflers, the same being connected in either thearmature circuit or the field circuit of the motor, a separate rectiiierbeing provided for each motor.

The present invention contemplates the use of novel means forcontrolling the grid circuits of the discharge devices in accordancewith the variations in the speeds of the individual motors from theirdesired or standard value, and, in its broader aspect, is applicablegenerally to control systems in which grid control vacuum devices areused. for speed control.

According to the invention, means are provided for damping the controlimpulses emav nating from a regulating unit associated with a sectiondriving motor, for affecting the grid circuit of the associateddischarge device to correspondingly aifect themotor controlled by, orsupplied with, power through the discharge device. Such regulating unitsmay comprise any means or devices that are actuated by the'diiierencebetween the standard or desired motor speed and the actual speed of theindividual regulated motor, and may comprise mechanical or electricaldiii'erentials jointly responsive to a master speed reference means forestablishing the desired speed of the regulated motors, and to theactual speed its associated regulated motor.

One advantage of grid controlled discharge devices,when used inautomatic control systems, is the quickness of response to controlimpulses from a controller eflecting correspondingly ystems forregulating the speeds of plural'motor drives,.-only when there is apossibility of adjusting the speed or rapidity of the transmission ofthe control impulse to the value which ditions of operation of themachine as a whole.

If a regulating unit for use with plural motor drives, such, forexample, as the differential element of a paper machine drive having a.standard speed shaft, is connected with a controller that is, in turn,connected in the grid circuit of a discharge device, and if thisdischarge device controls the circuit of an individual section drivingmotor of 'a paper making machine the effect of movements of thecontroller on the speed of the motor is very different from the actionobtained with the use of mechanical regulators when discharge devicesare not employed because of hunting action that is not usually presentwhen mechanical regulators are employed.

The reason for this appears to be due to the very high speed oftransmission of the control impulses by the discharge device which is acharacteristic of the device, giving it greater advantage overmechanical devices. Iif such a control system is provided with dampingmeans, the hunting will disappear and the control systern.- wlll operateproperly and much better and faster than other systems not provided withdischarge devices. The application and use of the present invention,therefore, makes it possible to take advantage of the characteristics ofdischarge devices to a much greater degree than heretofore.

An important advantage of the uniform speed '35 systemaccording to thepresent invention is that the system can readily'be adjusted to thedifferent control systems and drives than has heretofore been the case.It is well known that the requirements by a paper machine drive on a 40uniform speed system. are quite diiierent from those of a continuousroll drive for modern wire drawing rolls' that operate at speeds muchabove those of paper making machines. A paper making machine demandsgreat exactness of control 5 with respect to the adjustment of thespeeds of the individual motors and also with respect to the speeddifierences between the several motors, which must be very accuratebecause 01' the weakness of the web. In rolling or wire drawing mills,greater regulating speeds are required because of the greater workingspeeds of the material. Since, however, the material being drawn orrolled is quite sensitive .to irregularities in the drawing process,such as changes in the tension between the individual stands, it isnecessary that the motors be controlled very accurately.

Referring to the drawing,

Figure 1 is a diagrammatic view of apparatus and circuits illustratinga-preferred embodiment of my invention;

Fig. 2 is an enlarged view of damping means provided between thediiferential devices and the controllers;

Figs. 3 and 4 show other damping means for delaying the full effect of aregulating impulse upon the regulated motor, and

Fig. 5 is an enlarged cross sectional view of the shaft. driven by thedifferential element taken on lines V-V of Fig. 2 or 3 showing amechanical coupling between the controller driven shafts.

In the drawing a number of motors I, 2 and 3 are illustrated asconnected through mechanical gearing to rolls representing the separatesections of a paper making machine or a rolling mill. The motors l, 2and 3 are provided respectively with armature windings 4, 5 and 6 thatare supplied with current through electronic discharge devices I, 8 and9 that are each provided with three anodes ll, l2, [3 connectedrespectively to the conductors l4, l5 and iii of a three phasealternating current circuit supplied with power from a transformer l'l.Each of the electronic discharge devices I, 8 and 9 are provided with acathode I8 that is connected through the armature winding of itsassociated motor I, 2 or 3 and to a conductor I! that is connected by aconductor 2| to the neutral point of the secondary winding of thetransformer II. Each of the motors I, 2 and 3 is provided with a fieldwinding 22 shown as connected through a field adjusting rheostat 20 toany suitable direct current supply represented by the conductors 23.

Respectively associated with the anodes H, H and I3 of each of theelectronic discharge devices are control grids 24, 25 and 26 that areconnected to contact members or brushes 29, 28 and 21, respectively,mounted on a stator 3| of control devices 32, 33 and 34 associatedrespectively with the discharge devices 8, 1 and 3. Each control device32, 33 and 34 is provided with a rotor element and a movable contactmaking brush 35 carried thereby for engaging the contact members 21, 28and 29, the rotor brush 35 being connected through a slip ring andcontact member 36 to a conductor 31, that is connected through aresistor 38 to one terminal 39 of a resistor 48, the other terminal 4|of which is connected through resistors 44, 43 and 42, respectively, toconductors 41 48 and 45 that connect the contact members 21, 28 and 29,respectively, of the controllers to the grid members 26, 25 and 24 ofthe discharge device. A point 49 of the resistor 40, intermediate itsterminals, is connected by conductor 5| and through resistors 52, 53 and54, respectively, to the cathodes IQ of the tubes 8, I and 9. Theterminals 38 and 4| of the resistor 40 are connected, through groups ofrectifiers 55 and 55, to the three phases of a transformer 51 that is,in turn, connected to the conductors l4, l5 and I6 of the three phasealternating current supply circuit. The rotors of the severalcontrollers 32, 33 and 34 are connected to a common shaft 58 and drivenby an alternating current synchronous motor 53 having a three-phaserotor element 6!, connected through conductors 62 to the three-phasesupaooaoas ply conductors I4, I 5 and I8, and with two field windings 63and 64 that are displaced 90 electrical degrees on the stator'of themotor and are connected, respectively, through field adjusting rheostats55 and i5, and by conductors 51 and 68, to the direct current supplysource 23.

The power flow through the electronic discharge devices 1, 3 and 3 andthe motors I, 2 and 3 is determined by the position of the zero currentpoint in the alternating current wave of the source supplying thedischarge device with respectto the time of ignition, that is, to thephase displacement angle between the time of ignition and the time ofzero current, or the maximum value of the half wave of anode voltage. Anecessary condition for the proper operation of the discharge devices isthat the control means which determines the ignition time instant, thatis, which controls the periodic voltage variations in the gridcircuitmust remain in synchronism with the voltage supplied to the anodes. Thisis accomplished by connecting the rotors of the several controllers 32,33 and 34 to be driven by the synchronous motor 55 that operates insynchronism with the frequency of the circuit [4, l5 and I6 that isconnected to the anodes of the discharge devices. The two field windings63 and 84 provide two different excitation components that may beadjusted by the field regulating rheostats 55 and 66 to vary the angleof field flux with respect to the rotor SI of the synchronous motor,thereby varying the phase relation between the synchronous motor and itsalternating current supply to correspondingly vary the ignition timingof the discharge devices, and, consequently, the fundamental speed ofthe several motors I, 2 and 3.

One of the motors I may be selected as the guide motor to which thespeeds of the other motors of the system are compared and regulated. Itis desirable that the guide motor be selected as the one having thelargest rotating mass, or inertia, of the several motors of the group. Astandard generator 83 is connected through the cone pulleys 1| and 12 tobe driven in accordance with the speed of the motor I, and serves as amaster speed reference means for determining the speed of the regulatedmotors 2 and 3. The generator 58 is provided with stator windingsconnected by the circuit conductors 13 to the alternating current supplyl4, l5 and I6, and with rotor windings connected by conductors 14 to thestandard circuit 15. Each of the controlled motors 2 and 3 is providedwith a similar control generator 18 driven through similar cone pulleysin accordance with the speeds of the motors 2 and 3 respectively andhaving stator windings 11 connected to the alternating current circuitl4, I5 and I6 and rotor windings supplying an output frequency to theconductors I8.

Associated with each of the regulated motors 2 and 3 is an electricaldinerential 13 having a stator winding 80, energized in accordance withthe frequency of the control generator 18, op-

' erated by the section driving motor, and a rotor winding ll connectedto the standard circuit 15 and energized in accordance with thefrequency of the standard generator I! or master speed reference means.When the speed of the regulated motor 2 or 3 corresponds to its desiredvalue, thefrequency in the output circuit II from its associated controlgenerator 18, corresponds to the frequency in the circuit II. Avariation in these twofrequencies causes the electrical differential 19to operate in the one, or in the other direction, depending upon whetherthe frequency in the circuit 18 is greater than or less than that of thecircuit 15, and to correspondingly actuate a worm 82 that engages a gear83 connected to the stator portion 3I of the control device 32 or 34,and actuating the stator to move the position of the brushes 21, 28 and29 about the axis of the shaft 58 and correspondingly change the timingof theignition of the associated discharge device, thus changing thespeed of the motor driven therefrom. The stator portion of thecontroller 33, associated with the guide motor I, is stationary and thismotor is controlled only by changes in timing, as determined by changesin the phase relation of the synchronous motor 59 with respect toalternating current in the anode energizing circuit I4, I5 and I6.

It is desirable to provide damping means for damping the regulatingimpulses emanating from the differential devices and affecting the gridcircuits of the discharge devices to correspondingly afiectthe rate ofregulation of the motors 2 and 3. Such damping may be effected bymechanical means in the form of springs mounted on movable controlparts, as illustrated at 84, and shown in greater detail in Fig. 2 ascomprising a spring element 85 connected between shaft portions 81 and88 connected to the spring element 85 for driving the worm 82 inaccordance with the operation of the differential 19. The spring 85 is,preferably, made adjust able to suit different types of motorapplications. Another form of damping device is illustrated in Fig. 3,which shows a centrifugal rotating pump 89 mounted upon the shaft 81connecting the differential device I9 to the worm- 82, that, whenoperated, pumps a liquid through the circuit 9I, the resistance of whichmay be adjusted by a valve 92. Electrical damping means may also be usedconnected in the circuit between the controller and the control grids.The same result may also be obtained by damping means connected in theanode circuit of the discharge devices between the discharge device andthe motor operated thereby such as a reactor 93 shown in Fig. 4.

It may be preferable under certain circumstances to insure that thedamping means does not become effective immediately at the beginning ofthe regulating operation. Accordingly, the damping means illustrated aresuch that the control impulse is undamped at the first part of theregulating action and is effective after a certain time only. Thus, ifsudden changes of ,load occur on the motor energized through a regulatedgrid control discharge device, the con-' trol impulse sent out will atfirst be large and will thereafter decrease and finally become zero.

A further feature of the invention is the provision of means connectedbetween the regulating device and the grid control device for lim itingthe control angle or phase displacement between the grid voltage and theanode voltage,

82 and the differential 19 shown at 96 in Figs. 1, 2 and 3, and indetail in enlarged section in Fig. 5, as comprising the inner shaft 81driven by the differential device and an outer shaft 91 connected to theworm 82. The torque between the two shafts is transmitted by a ball 98which is held in the position shown by a spring 99. As shown as thebrush mechanism moves into the one or the other of its limitingpositions, and is held thereby the stop 94 or 95, the spring 99 willyield and the two shafts 81 and 91 will move relatively to one another.It is, of course, obvious that the same result can be obtained by otherequivalent means. H

In operation, the motors I, 2 and 3 are brought to a fundamental uniformspeed as follows. Contactmaking device I00 is closed and transformer ITis energized and supplies power to the con ductors I4, l5 and I6 of athree-phase alternating'current circuit. When the .conductors I4, I5 andI6 are energized, current is supplied to the rotor element 6I ofsynchronous motor 59 through the conductor 62 from the conductors I4, I5and I6. The field windings 63 and 64 of the synchronous motor 59 areenergized from the direct-current supply source 23.

The excitation components of the field windings 63 and 64, which aredisplaced electrical degrees on the stator of the motor 59, arecontrolled by adjusting the field rheostats 65 and 66, which areconnected by conductor 61 to one of the conductors of the direct-currentsupply system 23 and by conductors I M and I02, respectively, to thewindings 63 and 64 through conductor 68 to the other conductor of thedirect-current supply 23. By adjusting the rheostats 65 and 66, theangle of field flux is varied with respect to the rotor 6| of thesynchronous motor and the phase relation between the synchronous motorand its alternating-current source is varied. The synchronous motor 59drives the shaft 58 to actuate the rotors of the contact control devices32, 33 and 34. The purpose of the contact control devices will be ex-'plained hereinafter.

When the alternating-current supply conduc- 4 tors I4, I5 and I6 areenergized, transformer 51 connectedthereto is also energized. Thetrans.- former 51 is connected through rectifiers 55 and 56 to aresistance 40 to provide a constant source of potential, the purpose ofwhich will be explained hereinafter.

In order to supply current to the armatures 4, 5 and 6 of the motors I,2 and 3, the circuit closing members I03, I04, and I05 are actuated tocontact making position. The actuation of circuit closing member I03completes a circuit from the alternating-current source I4, I5 and I6through conductors I06, I01 and I08 and the circuit closing member I03which is connected to the anodes II, I2 and I3 of the thermionicdischarge device I by conductors I09, H0 and I I I through the dischargedevice I to its cathode I8, which is connected by conductor II2 to thearmature 4 of motor I and thence through conductor II3 to the neutralconductor I9, which is connected by conductor 2I to a neutral terminalof the secondary winding of transformer I1. Similar circuits for passingcurrent to the armatures 5 and 6 of motors 2 and 3 are completed uponactuation of circuit closing members I04 and I05. The excitation of thefield windings 22,

.ofeach of'the motors I, 2 and 3 is varied by adjusting the resistor 20.One terminal of the field winding 22 is connected tothedirect-cur- .75

rent supply system 23 by conductor lit and the other terminal isconnected by conductor H5 through the rheostat 20 and conductor lit tothe other conductor of the direct-current supply 23.

The amount of current conducted througheach of the thermionic dischargedevices I, I and 2 to the armatures 4, 5 and 6, respectively, dependsupon the potential impressed upon the grids 24, 2! and 20 of each of thedischarge devices. As shown, the discharge devices employed in thisinvention are of theconventional gas filled type, wherein there isconduction from the anode to the cathode when the grids have a negativepotential impressed upon them. The grids 24, 28 and 2! are connectedthrough conductors ll, It and I1 and resistors 42, 43 and ll,respectively, to the positive potential terminal I of the constantsource of potential by conductor I", so that a positive potential isimpressed on the grids at all times.

If a negative potential is impressed upon the grids. the dischargedevice becomes conductive at the period in the positive cycle of thealternating-current source at which the negative potential is impressedupon the grid and will act to conduct current to the armatures of therespective motors during the remaining portion of the positive cycle ofthe alternating-current source. By providing each discharge device withthree anodes and three grids, one for each phase of thealternating-current source, the tube functions to conduct a continuouscurrent to the armatures of the motors.

The amount of current conducted through the discharge device to thearmatures is regulated by the contact control devices 22, I2 and 24,which are operated by the synchronous motor 50 in synchronism with thealternating-current source. 'Ihe contact control devices 22, 22 and 24function to complete a circuit from the cathodesllofeachofthedischargedevices Llandl through conductors Ill, resistorsll, 2 and I4. respectiveb, and conductor II to an intermediate terminalI. of the resistor ll, which is connected at its negative potentialterminal 22 through a resistor 22 and conductor 21 to the contact member20 which is connected through a slip ring and the rotor brush ll tocontact members 21, 2! and 22 positioned on the stator of each of thecontact control devices 22, 23 and II and connected through conductorsll, 46 and 41 to the grids 20, 2| and 20, respectively. Since thecontact control devices 32, I2 and 24 operate in synchronism with thesynchronous motor I, the period in the positive cycle of thealternatingcurrent source at which brush II contacts the contact members21, 22 and 2! is adjusted by varying the phase relation of thesynchronous motor II with respect to the alternating-current source toeither cause the contact of brush 2! and contact members 21, 22 and 22to lead or lag the alternating-current source and thus to vary theperiod in the pomtive cycle of the alternating current source at whichthe negative potentialisirnpresseduponthegrids24,2land2t of thedischarge devices to vary the amount. of

'currentconductedtothearmaturesLIandl,

and to thus vary the fundamental uniform speed of the motors i, 2 and 2.

Whenthemotors l,2andlareoperatingat a uniform fundamental speed, theoutput of generator I connected bycone pulleys Ii and 12 to the motor i,and the output of generators 18 cimnectedtothemotorslandiareequaLand 21and I! to move relative to one another.

it is evident that the frequency oi the stator winding ll of thedifferential 19 connected to the generator 16 by conductor II and thefrequency of the rotor winding ll of the differential l9 which isconnected to generator 60 by conductors II and 14 is balanced, and thatthere will be no tendency of rotor 8! to be actuated to adjust thestator of the contact control device.

Assuming that the load upon the rolls operated by motor 2 is increased,the speed of the motor is decreased with a consequential decrease in thespeed of the generator it operated thereby. Thus the output of thegenerator is decreased, and the frequency of the stator winding ll ofthe differential I! connected to the generator Ii by conductor II islowered. Since the frequency of the rotor ll of the differential 18connected by means of conductors I5 and 14 to the generator 69 of theconstant speed motor I has not been changed, there is an unbalancedcondition between the stator and the rotor II which will tend to actuatethe rotor and to function, through the shaft 22, spring ll, shaft 21,shaft 21, worm 22 and the gear 22, to so position the stator ii of thecontrol device 22 as to advance the brushes 21, 22 and 22 to a positionwhere contact with brush II is made at an earlier period in the positivecycle of the alternating-current source to impress an advanced negativepotential upon the grids 24, 2i and 26 to allow more current to pass tothe armature winding 5 of the motor 2.

As the speed of motor 2 and generator 12 is increwed, the frequency ofthe stator III of the differential II is increased and approaches thatof the rotor ll controlled by the standard motor I until a uniform speedof the motors and a balanced condition in the differential 1! has beenreached, and the operation of the control device 32 to shift the brushes21, 22 and 29 ceases. Under such conditions, the control device 22eifectiveiy controls the ignition timing of the electronic dischargedevice 2 to maintain motor 2 at the same speed as standard motor I. Thusthemotor2isspeededuptothedesiredconstant value of motor i.

Extreme movement of the stator 2| in response to a regulating movementof the differential II is limited by the stop 24 or II. When the sector23 abuts the stop 04 or SI, the mechanical connection between the wormgear '2 and the differential functions, through the yielding spring 02,to disperse the torque by allowing the shafts This arrangement preventsthe movement of the stator ll and brushes 21, 22 and 2! to a point whereonly the maximum or minimum negative potential desired is secured.Otherwise, if the stops 2 and were not provided on the stator, thestator would move so that contact of the brushes would first be made atan earlier period in the positive cycle of the alternating-currentsource and the movement of the stator would continue until contact ofthe brushes was made at a later period and the opposite eifect from thatdesired would be secured.

It is to be noted that, if only a momentary decrease in the frequencyoutput of generator I! is eflected, the rotor II will not eifect adisplacement of the stator II of the control device 32, for themomentary operation of the rotor ll will be taken up by the spring 2!rather than be transmitted to the worm l2 and the gear 22, thuseifectively damping any momentary or hunting impulses of the motor 2.

If the load upon the rolls operated by the motor 2 should be decreased,the speed of the 76 motor 2 increases with a consequential increase inthe speed and output oiE the generator 16, which, operating through itsoutput circuit 18, effects an increase in the frequency of the stator80, thus creating an unbalanced condition in the differential l9 andtending to, actuate the control device 32 i i-a direction to shift thebrushes 21, 28 and 293" so that contact with the brush 35 is made at alater period in each of the positive cycles oi alternating-current fromthe source l4, l5 and iii to impress a retarded negative potential uponthe grids 24, and 26. The retarded negative potential impressed on thegrids 24, 25 and 28 reduces conduction in the discharge device 8 andlowers the power input to the motor 2, thus effectively reducing thespeed of motor 2 to the desired speed of the standard motor I.

Control of motor 3 is effected in a similar manner as that of motor 2.

Modifications in the circuits and apparatus il-' power source, a gridcontrolled vapor discharge device associated with each motor forsupplying direct current power to the motor from said alternatingcurrent supply, a diflerential device associated with each regulatedmotor and responsive to variations in the speed thereof from its desiredvalue, a contact controller device associated with each [difier'entialdevice and responsive to an unbalanced condition therein for modifyingthe control impulses to the grid of said discharge device to correct themotor speed, and damping means connected between the diflerential deviceand the contact controller device for effecting movement of the contactdevice. i

2. In a regulator system wherein a plurality of motors are required tooperate in a predetermined speed relationship, a master speed referencemotor and a motor to be regulated with respect thereto, an alternatingcurrent power circuit and grid controlled electronic discharge devicesconnected thereto for supplying direct current power to'said motors,control means actuated in synchronism with the frequency of saidalternating current circuit for effecting the ignition of said-dischargedevices, means for varying the timingof ignition of the discharge devicesupplying power to said regulated motor in accordance with its variationfrom its desired speed, and a synchronous motor energized from the samecircuit as the anodes of said electronic discharge device for actuatingsaid control means characterized in that the relative position of therotor and the rotating field of the synchronous motor is adjustable forthe purpose of varying the fundamental speed of the system.

ERWIN JANETSCHKE.

